Braking at the Boiling Point

Combatting brake fatigue on the track or deep in an off-road course comes down to effectively fighting the high temperatures associated with heavy braking use. While typical day to day driving might have your brake rotors and pads reach a balmy 400 degrees Fahrenheit, racing applications quickly reach into a 600 to even 1500 degrees.

Lower boiling point brake fluids found in non-race specific formulas generate air bubbles as the brake fluid exceeds its temperature limits. These bubbles are what you feel when your brake pedal compression becomes soft. DOT 3, 4, and 5.1 formulas feature a wet and dry boiling point. In terms of fresh brake fluid the dry boiling point is the number to look for. Over time, however, these fluids become susceptible to water absorption, which is why DOT standards include the wet boiling point.

For your specific application, it is important to evaluate your performance needs.

MOTUL RBF 600 Brake Fluid

Extreme high-performance polyglycol brake fluid. Far exceeds the standards of DOT 4. Each bottle is filled with Nitrogen, increasing shelf life and eliminating contamination while factory sealed. Extremely high dry boiling point 594F(312C) helps prevent vapor lock and brake fade during hard use, with excellent recovery time.

The very high wet boiling point (204°C / 399°F) superior to conventional DOT 5.1 non-silicone base fluid (180°C / 356°F mini) and DOT 4 (155°C / 311°F mini) enables to keep an efficient brake system when rainy. Indeed, DOT 3, DOT 4 and DOT 5.1 brake fluids have the property to absorb humidity in the air, which reduces their boiling points and increases the risk to get to “vapor lock” phenomena. The wet boiling point is measured by humidifying the product with about 3.5 % of water.

Spectro Performance Oils – DOT 4 Racing Brake Fluid “600”

Designed of a borate ester polyalkyglycoalkylether formulation in order to provide the highest possible resistance to fluid boiling and degradation in high performance and racing conditions, Spectro® DOT 4 Racing Brake Fluid “600” is described by Spectro as your best defense against “lost” lever pressure caused by progressive heat buildup. Spectro DOT 4 surpasses DOT 4 specifications feature a 599 degrees Fahrenheit dry boiling point, it solves virtually any fluid boiling problems hard driving can create. Excellent for on- and off-road applications.

CASTROL REACT SRF BRAKE FLUID

The compressibility of Castrol React SRF Racing is very similar to that of current DOT 3 and DOT 4 fluids. It can, therefore, be filled into any braking system used in motorsport with the exception of those for which a mineral oil is prescribed. It gives a “hard pedal” feel. Widely used in racing, from Formula One, sports cars, V8 Supercar and Grand Prix and Superbike motorcycles. The exceptionally high dry boiling point (higher than 300°C) makes Castrol React SRF Racing ideal for use under arduous braking conditions such as rallying or racing. It exceeds the boiling point requirements of DOT 5 brake fluids. Castrol highly recommends for cars used for “Club and Track days”

Brembo LCF Plus Brake Fluid

Brembo LCF 600 plus Brake Fluid has been formulated to provide the highest performance in all racing conditions and has an independently proven low compressibility at high temperatures. Brembo LCF 600 plus fluid also resists boiling at higher temperatures (both wet and dry) over other race fluids. Typical dry boiling point is 601°F and wet boiling point 399°F. Brembo’s LCF Plus exceeds the requirements of U.S. FMVSS 116 DOT4 specifications and mixes safely with DOT3, DO4 and DOT5.1 racing brake fluids. It is not suitable, however, for use in brake systems containing magnesium parts.

Wilwood EXP600 PLUS Brake Fluid

Wilwood EXP Super Hi-Temp 600 Plus Racing Brake Fluid has been specially formulated for racing applications where brake systems consistently operate at very high temperatures. In addition to guarding against vapor lock, EXP Super Hi-Temp 600 Plus Racing Brake Fluid maintains its viscosity and lubricity under extreme temperatures for maintaining brake system reliability and performance. EXP Super Hi-Temp 600 Plus Racing Brake Fluid conforms to, and exceeds U.S. specification FMVSS No. 116 DOT 4. Typical dry boiling point: 594° F (312° C). Typical wet boiling point: 399° F (204 °C).  It is true that racing fluids need to have high boiling points. It is also true that fluids need to have low moisture affinity to slow the natural absorption rate of water vapor. But the true test of any fluid is how well it resists aeration and compressibility after it has been heated and pressure cycled a few hundred times. According to Wilwood, the real test is at the track. EXP has been proven to maintain firm pedal feel and quick response, long after others have failed.

A Fluid Stop

In terms of best braking fluid, the choice revolves more on the amount of brake use you foresee in your future. Precise control of your brakes and eliminating the loss in feedback from when your brakes are hot and overworked is paramount. Be sure to perform a proper bleeding of your brake system between fluid changes to maximize braking response.

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Sources:

Brembo: www.brembo.com

Castrol: www.castrol.com

MOTUL:  www.motul.com

Spectro Performance Oils: www.spectro-oils.com

Wilwood Disc Brakes: www.wilwood.com